In internal combustion engines, it is conventional to initiate combustion with the use of spark plugs. In conventional spark plugs, a body which defines a longitudinal axis is provided. The body has, adjacent one end thereof, a metal ring which is orientated coaxially with the longitudinal axis. The body further includes a metal tube which: is orientated coaxially with the longitudinal axis; extends from the ring towards the other end of the body; and is externally-threaded for engagement in a corresponding threaded bore in an engine block in use. A porcelain insulator also forms part of the body. The insulator has a portion disposed inside the tube. This portion extends axially, from inside the tube, beyond the ring, and has an elongate void extending axially therethrough. An elongate positive electrode occupies the void and extends axially beyond the insulator to a terminus which defines the one end of the body. Conventional spark plugs also include an electrode leg. The electrode leg has two arms transversely connected to one another, with one arm extending axially from the ring and beyond the electrode and the other arm extending radially inwardly from the one arm so as to terminate in an end portion that is axially-spaced from the terminus. The spark gap in this conventional plug is the space defined between the positive electrode and the electrode leg.